Reducing CM Conducted EMI in ISOP Flyback Converters Through Balancing Technique

In high-voltage to low-voltage isolated power con- verters for automotive applications, a promising topology is the Input-Series Output-Parallel (ISOP) flyback, allowing to reduce the voltage stress on power transistors. However, Common-mode (CM) conducted Electro-Magnetic Interference (EMI) for such a topology has not yet been thoroughly addressed. This paper investigates the CM EMI reduction at the source by exploiting symmetrical topology combined with balancing technique tai- lored for ISOP topology. Based on the employed CM equivalent model, the required balancing conditions are derived, leading to a double capacitive compensation which ensures complementary switching waveforms. Simulation results validate the proposed model, allowing a significant CM conducted EMI reduction.